Photographic light-sensitive material and process of making the same



Patented Mar. 2, 1926.

UNITED STATES PATENT; OFFICE.

samunnn. sum-Penn, or ROCHESTER, NEW YORK, ASSIGNOR 'ro msm m KODAK COMPANY, or ROCHESTER, NEW YORK, A CORPORATION on NEW YORK.

PHOTOGRAPHIC LIGHT-SENSITIVE MATERIAL AND PROCESS OF MAKING- THE i No Drawing. Application filed June 6,

To all whom it may concern:

Beit known that I, SAMUEL E. SHEPPARD, a subject of the King of Great Britain, residing at Rochester, in the county of Monroe and State of New York, have invented certain new and useful Improvements in Photographic Light Sensitive Materials and Processes of Making the Same, of which the following is a full, clear, and exact specification.

This invention relates to the art of photographic materials.

One object of the invention is toprovide photographic emulsions, especially developing-out ones, having new or lmproved properties because of the use or presence thereinof materials, the sensitizing properties-of which I have discovered. Still another-object of my invention is to provide processes in which such materials are used to improve photographic emulsions, especially developing-out ones, as regards lightsensitiveness, by which term I include their ability to give the earliest visible impression or image with'the minimum exposure or their ability to give density after a given exposure or both, the usual photographic fluid treatments being used in preparing such impression or image or density.

A further object of the invention is to provide colloid products, such for instance as gelatins, the usefulness of which for forming light sensitive photographic emulsions, especially developing-out emulsions, is greatly increased and controlled by my said sensitizing materials incorporated therewith. Another object of the invention is to provide processes for preparing said colloid products or intermediates.

Other objects are,to increase the sensitiveness of photographic emulsions, especially developing-out emulsions, while wholly or partially dispensing with expensive or long and uncertain socalled ripening methods; to enable the use ofa type of gelatin having desirable physical qualities in making such a photographic emulsion of greator light-sensitiveness than that normally obtainable with said gelatin; to obtain more stable emulsions through the purity of the ingredients; to increase the light-sensitiveness of photographic emulsions, particularly developing-out ones, the grain characteristics of which have already been determined ;v to increase the general light-sensi- 1924. Serial N0. 718,411.

tiveness of such photographic emulsions throughout the spectral ranges to-which they are normally sensitive; to make such photographic emulsions of standard light-sensitive characteristics with gelatins which'normally do not produce emulsions having such characteristics; to make, as intermediates .in,the, manufacture of photographic "emulsions, gelatins of standard light-sensitiveness giving power out of gelatins which do not normally have the power of giving such standlight-sensitizing effects upon photographic emulsions, especially developing-out ones, when incorporated therein. Broadly speakmg each compound of these series contains a divalent atom of the sulfur group (a sulfur atom in one series, a selenium atom in another series, a tellurium atom in still another series) which is joined by adouble bond to a singlemetalloid atom (not one bond to one atom, and the other bond to a different atom) to which at least another groupof atoms is attached. Generally it is desirable that the last mentioned group of atoms be such that it induces in the compound a chemical affinity for silver halids,-for instance the compound may combine to an. appreciable extent with silver halid to form a soluble complex salt, when said atomic group is present. Moreover, the metalloid'atom to which the atom of sulfur, lurium is joined by a double bond is in many instances, but not necessarily, a carbon atom.

For some of the invention, I select following subseries,thiocarbamids, seleno car-bamids, and tellurocarbamids. As the corresponding carbimids are likewise usable in preferred examples of my invention and are readily changed into' said carbamids, espccially for instance in emulsions of the alkaline or ammonia type, it wi'H-"be understood that the corresponding ca'rbimids are included hereinafter when said carbamids are claimed. These subseries of carbamids and carbimids includemany compounds containing one or more substituent radicals,

preferred examples of my selenium, or telfrom the above series the ourea (thiosinamine) containing an allyl radical in place of one of the hydrogen atoms of thiourea, is especially useful in practicing my invention. So are allyl isothiocyanate,

allyl isoselenocyanate, allyl selenourea, and

I together to obtain their mutual or cumulative effects.

It is a common characteristic of the compounds which I use, that said double bonded atom of the sulphur group is chemically held in the molecule with intermediate firmness. Such atom does not react on silver halids as readily as the sulphur atom in sodium sulphide for instance, but it separates out more readily than the sulphur atom in ethyl mercaptan for example. Consequently said double bonded sulphur-group atoms in my compounds correspond roughly in the firmness with which they are held to the firmness with which the sulphur atoms are held in the so-called potential mercaptans, although there is, of course, some range of difference in the firmness with Which said doublebonded atoms are held in the different compounds of my series. The sensitiveness of the grains of silver halid in emulsions has 'been shown to correspond to the presence in said grains of nuclei of unstatedvchemical composition. I, therefore, attribute the sensitizing action of my compounds to their forming in the emulsion grains small, mostly ultramicroscopic, nuclei. which includes silver combined with either sulfur, or selenium, or tellarium, such as silver sulfid,

silver selenid, and silver tellurid. The intermediate firmness with which said doublebonded atoms-are held in my compounds except as defined in the claims.

I have also found that the proportions in which my compounds are incorporated in the emulsions (or in the colloids for the emulsions) are important. If used in too high concentrations, they cause fog, and sometimes reversal. The largest proportions which can be effectively used vary somewhat with the particular sensitizing compound or compounds which are used. with the proportion of gelatin to silver halid inv the emulsion, with the type of emulsion as regards grain size characteristics and alkalinity with the amount of natural sensitizer originating in the gelatin when the latter is manufactured, with the particular silver halid or halids employed, the standard as regards fog which is set by the emulsion maker, etc. This maximum pro ortion is in any specific case easily found, being about as readily determined by routine test as, for example, the proportion of sulfur permissible in steel for a particular purpose. It is, however, always surprisingly small. In gen-. eral with gelatino-silver-halid developingout emulsions, it should be'less than about causes immedite fogging tendency should not to be'used,-that is, a quantity which causes more than the tolerated fog allowed in the particular type of emulsion in the. trade after the customary allowed period of storage. I have found 2 to 3 grains of sensitizing compound, such as thiosinamine for instance, to 100 pounds of gelatin (computed as dry) or 130 pounds of emulsion (computed as dry) is within the useful limits and generally excellent,say for instance with alkaline developing-out gelatino-silver-halid emulsions. Of course, smaller amounts of seusitizers are employed when less sensitizing effects are desired; but it is important not to exceed the upper limits as stated above.

Because only very minute quantitcs of my sensitizing compounds are used, (often less than one three hundred thousandth of theweight of emulsion) the addition of them does not appreciably dilute the emulsion or emulsion-forming colloid; nor does it affect their physical properties. Consequently the use of my compounds provides a novel, dependable and independent way for control ling the properties of photographic emulsions in addition to the customary expedients hitherto available. Gelatins, for instance, can be selected for their physical properties, such as setting ability, melting point and viscosity, without regard to whether they can be made into suflis-iently light-sensitive emulsions, and any deficiency insensitizing power can be made up by in corporating a little quantity of one or more of my independent compounds. .Nor are the grain-size characteristics affected by such id in the emulsions which is independent of the ratio of gelatin to silver halid. Still differently stated. the sensitizer compounds can be added without adding any colloid, such as gelatln, and are, therefore, independent thereof. i

lengths. Unlike the effects, of dyes, the sen sitiveness is increased throughout the normal spectral range of the emulsion instead of at only those spectral points corresponding to the spectral absorption of the sensi-' tizing compound. My compounds are effective in increasing the general light-sensitiveness of orthochromatic, panchromatic, X-ray, and all special emulsions, as well as the ordinary or non-color-sensitized ones. They can be added without 'or with sensitizing dyes or before or after them. They do not specifically affect the dye action; but simply increase the general sensitivenessand thus increase the ordinary sensitiveness to blue light to at least as great an extent as to light of a color corresponding to the dye.

My sensitizing compounds may he used in many ways. Broadly they may be incorporated in emulsions or incolloids for emulsions or both. They can also enter the emulsion mixed with other ingredients thereof whether organic or inorganic. They may be added at different stages of emulsion manufacture, even when the latter is otherwise complete ready for coating. Since their action is rapid when incorporated, the coating in such case need be delayed only long enough to mix in the sensitizing compounds. With the grain characteristics, such as size distribution, etc., already determined, and the other physical and photographic properties of the emulsion already taken care of at this stage, I can practically independently increase its light sensitiveness without impairing said other properties by adding one or more of my compounds. The latter are especially effective in emulsions which are, at least slightly, alkaline.

Where different batches of emulsion, especially developing-out emulsions, fall below a required manufacturing standard of light sensitiveness, although they may be otherwise satisfactory, their sensitiveness can readily be brought up to standard by mixing in my sensitizing compounds, theproportion varying with the increase necessary to produce a uniform product. Emulsions having almost no practical light sensitiveness but having enough other desirable qualities can, be made usefully light-sensitive by my compounds. Thus the la ter are useful in connection with emulsions having good initial light-sensitiveness and those having almost no initial sensitiveness. The

increase -1n sensltlveness can be effected in one step by thoro'ughly'stirringall of the sensitizingcompound into the emulsion at one time; or it may be incorporated part at a time in successive steps. When making new batches of emulsion from the same materials which have yielded deficient ,emul s ons, correctional quantities of my s'ensi-,- tizing compounds can be premixed withan mgredient, such as gelatm.

The following example illustrates how light-sensitive photographic emulsions ofthe developing-out type may be prepared and improved by the aid of one or more of my sensitizing compounds. invention is not restricted to this illustration, except as indicated in the claims. The emulsion-forming operations hereinafter described are along the-lines of known practice, see for instance Die Photographie mit Bromsilber Gelatin by J. M. Eder, published in Halle, Germany in 1903by Wil- Of course, my 1 helm Knapp as Part III of Eders Ausfiihrliches Handbuch der Photographic.

The two following-solutions are made up, the parts being by Weight: I

900 parts of silver nitrate in 9, 200 parts of water.

In mixing B, the halid 'saltsare' first dissolved, the Water and the gelatin then added to the salt solution. Solution B is then warmed, say to 140 F. or 150 F-. for example; and the silver nitrate solution A is gradually added to it with constant stirring. It is preferable to' warm solution'A before adding it to B, say to 150 F. or 160 F. for instance. -Vhen solution A has been thorougly incorporated in solution B, there are then added 43 parts of strong ammonia previously-dissolved in 900 parts of water. The emulsion formed by these operations is allowed to stand'for a short time; say 15 minutes to a half hour for example. Then 1050 parts of gelatin are dissolved in it with thorough mixing. The emulsion is next cooled, such as'by keeping in a cool space,

a short time, say a few minutes. It is then cooled and set.. It is an example of the amalkaline type of developing-out pared emulsion, th' are most conveniently handled by dissolf ng them in a solvent which is inert with respect to the emulsion and simply acts as a-vchicle to help in spreading the compounds throughout the emulsion. So long as an even distribution of the compounds throughout the emulsion is effected and the correct proportion of them is added, their particular concentration in the solvent or vehicle is not important. It is good practice to keep the volume of the solution added to the emulsion under 2% of the volume of the emulsion; but this isnot indispensable. For example, where 1 part of thiosinamine by weight is to be incorporated into 300,000 parts by weight of the above described emulsion (computed as the weight of its non-aqueous ingredients) the emulsion is melted, the thiosinamine dissolved in ethyl alcohol or water or a mixture of them, the volume of said solvent being under approximately 1.5% 'of the volume of r the melted emulsion, and then the solution mid, thiobarbituric acid, telluro-mustard-oil (allyl isotellurocyanate) potassium tellurocyanide, allyl tellurourea. It is preferable to use these compounds in substantially pure or C. P. form; but impurities which are harmless to the emulsion and are not bulky, can be tolerated. The selenocyanide and tellurocyanide are used in-higher proportions than the other listed compounds.

\Vith its light-sensitiveness increased by my compounds, the emulsion, being melted to the desired flowability, is coated on its support, such as glass, film, paper, etc., in the well known way. It is convenient to control and checkthe process by coating samples of the emulsion before and after the addition of mypse'nsitizing compounds, the coated specimens beingtried out photographically by any well known sensitometric test, or even by comparative camera exposures on the same subject under like conditions. Of course, the usual precautions are observed during the emulsion making and coating processes, such as the use of non-actinic or safe light, cleanness of vessels and air, etc. I

The different gelatines sold for photographic emulsion-making may be ,used in the example given above, hard ones being very useful. The temperatures given are, of course, adjusted if the particular gelatin employed has physical properties, such as melting and setting points, which deviate considerably from the usual ones, such adjustment being a matter of routine control.

Instead, however, of using gelatines which give emulsions of useful but lower sensitiveness even before the addition of my sensitizing material, an almost inert gelatin may be employed,one which-forms an emulsion which produces a developable image, if at all, only after impractically long exposures, and then does not yield an image of desirable density. A gelatin which forms such a practically inert emulsion may be prepared in the way described under the heading Preparation of ash-free gelatin in pages 1850 and 1859 of the Journal of the American Chemical Society, September, 1922, Vol. XLIV, N0. 9, being part of an article by Sheppard, Sweet, and Benedict on Elasticity of purified gelatin jellies as a function of hydrogen-ion concentration. Emulsions of impractically low light-sensitiveness made by the above described process from such prepared gelatin, are transformed by my sensitizing compounds into emulsions which give developable images of excellent density after usefully brief exposures. I have, for example, been able to increase the light-sensitiveness of some such low sensitiveemulsions ten or even over twenty times, the exposures for a given subject in the latter case being cut to less than one twentieth of the original one and the image density being ma e excellent by I a corresponding gain. Increases of the same general order of magnitude are made when my sensitizing compounds are added in similar proportions to emulsions which are made from normal photographic-gelatins or mixtures of such normal gelatins with said almost inert gelatins, and already have useful, but lower initial sensitiveness. Different percentages of sensitizer produce correspondingly different increases. The increases in developingout emulsions appear upon the usual developing operations. Customary pyro and metol-hydrochinon alkaline developers are suitable for example. An inert emulsion prepared as above described is a very useful medium or standard in which to test the sensitizing properties of different com- V cording to the reference given inthe precedcal properties.

ing paragraph, I can prepare inert gelatins by treating active photographic gelatins with oxidizing agents. The latter oxidize the sulfur in the sensitizing substituted (allyl) thiocarbamide or corresponding carbimide, which occurs naturally in photographic gelatins, thus converting it toa nonsensitizing compound and leaving the gelatins practically inert. Dilute aqueous solutions of a peroxide, such as sodium peroxide (say from 5 to 10% by weight) is intimately mixed into the gelatin and then washed out when the oxidation has occurred. The inert gelatin referred to in the preceding para-- graph can be thus oxidized to make its inertness doubly sure.

lVhen preparing inert gelatin on a considerable scale, it is far preferable to introduce the oxidizing step during the regular manufacturing. operations, say the liming and/or deliming treatments. The oxidizing agents should be effective as desensitizers and yet not be present in quantities capable of materially reducing the yield of gelatin or harming its quality, especially its physi- Nor should they leave ob jectionable products from the oxidation re-- action. For example, the regular liming solution of the usual gelatin manufacturing process can b e saturated with as much calcium hypochlorite as will dissolve therein;

' or it can contain about 5't-o 10% of sodium peroxide. Subsequent operations then pro ceed as usual.

My sensitizing compounds may be incorporated into gelatin from which photographic emulsions are to be. made. v This strengthen'edgelatin then constitutes a facture.

thus treated, that which has been rendered valuable intermediate in emulsion manu- While any good gelatin may be inert by the above described'oxidation treatment during liming or deliming is particularly ada ted to this strengthening. Emulsions ma e fromth'e mixture have markedly increased light-sensitiveness as compared with those. made from corresponding unstrengthened 'gelatins. The proportion of sensitizing material is, of course, adjusted to give the desired controlof the sensitiveness of emulsions made fromthe gelatin, the totalsensitizing material in the strengthened gelatin being thus brought to, or even above, normal. a

When Working on a considerable. scale,

this activating of gelatin, such, for instance, as said inert gelatin, is one of the most desirable ways of employing. my sensitizing compounds. In fact, premixingof one or more of my sensitizers with gelatm is my preferred system. During manufacture of the gelatin, say for instance when the 'con- For example 2 or 3 grains of thiosinamine or any of the hereinabove listed compounds or mixtures of them is carefully mixed with each fraction of gelatin solution containing pounds of gelatin (calculated as dry). The comfpound, say thiosinainine, is takenup, pre erably in as little aqueous-alcohol mixture as is practicable, and then this concentratedsolution added to the gelatin solution. In this way'imdesirable dilution of the latter is avoided.

Ona large scale, the s'ensitizing'solution may be accurately and continually dosed into a regulated@ stream ofgelatin solution with continuous mixing. Alternatively dried or set gelatin may be allowed to swell in an aqueous solution of the sensitizing compound. The nearly uniform distribution or diffusion of the compound in the gelatin thus efi'ected can be made even more nearly uniform by melting and agitating the swollen gelatin.

In'the examples given above, the steps of treating With ammonia and warming of the emulsion just before its final setting improve the photographic properties of the emulsion, especially when the latter is made from hard gelatins. But one or both of them maybe omitted. In other words, my sensitizing compounds act by themselves to. increase the light-sensitiveness, whether ripening steps be employed or not, and so can wholly or partially replace them. But I prefer to use them because the effect of either or both of them is to help increase the light-sensitiveness of the emulsions and thus give a stronger initial sensitized condition which is multiplied or increased by using my sensitizing compounds. When using any of the inert gelatins mentioned above an making very; sensitive emulsions, these steps can sometimes be shortened and made more certain in effect by reason of the use of my powerful and dependable sensitizing compounds. 1

I have described gelatin emulsions and emphasized the developingout and alkaline types because at the present time they are l the ones, which have the widest practical use. Moreover they form the best medium for testing new sensitizing-compounds. But other organic colloids and mixtures of them with each other or with gelatin, where their nature admits such mixtures, may be used in making light-sensitive emulsions which of the others. Y

aving thus described my invention, what I claim as new and desire to secure by Letters Patent is: 1. A photographic emulsion comprising a colloid, particles of photographic silver salt suspended therein, and an added compound therein upon which at least part of the lightsensitiveness of the emulsion depends,

said compound containing a divalent atom of the sulfur group directly joined by a double bond to a single metalloid atom, -to which at least another group of atoms is attached, the pro ortion of said compound being substantiall'y independent of the proportion of said colloid.

2. A photographic developing-out emulsion comprising a colloid, particles of silver halid suspended therein, and an added compound therein upon which at leastpart of the light-sensitiveness of the emulsion depends, said compound having a chemical affinity for silver halid. and containing an atom of the sulfur group joined to a single metalloid atom,.to which at least another group of atoms is attached, the presence of said last named group inducing saidchemical afiinity, the proportion of said compound being substantially independent of the proportion of said colloid.

3. A photographic developing-out emulsion comprising gelatin, particles of silver halid suspended therein, and an added compound therein upon which at least art of the light-sensitiveness of the emulsion de pends, said com ound containing a divalent atom of the sulfur group directly joined by a double bond to a single carbon atom to which at least another group of atoms is attached, the proportion ofsaid compound being substantially independent of-the proportion of said gelatin.

4. A photographic developingout emulsion comprising a colloid, particles of photographic silver salts suspended therein, an added-compound which orms small ultra-' microscopic nuclei of a silver compound containing an atom of the sulfur group, said nuclei being located on said particles of silver halid, the proportion of said compound being substantially independent ofthe proportion of said colloid.

5. A photographic developing-out emulsion comprising gelatin, particles of silver halid suspended therein, and an added senat least part of the light sensitiveness of the emulsion depends, the propprtion of said thiocarbamid being substantially independent: of the proportion of gelatin,

6. A photographic developing-out emulsion comprising gelatin, particles of photographic silver salt suspended therein and thiosinamine added therein upon which at least art of the li ht-sensitiveness 'of the emulslon depends, file proportion of said thiosinamine being substantially independent-of the proportion of said gelatin.

7. A photographic developing-out gela tino-silver-halid emulsion of the alkaline type of relatively high light-sensitiveness, comprising a mixture of the constituents of a gelatino-silver-halid emulsion of lower light-sensitiveness, and an added sensitizing compound upon which depends the difference between said lower and said high light-sensitiveness, said compound containing a divalent atom of the sulfur group directly joined by a double bond to a single metalloid atom to-which at least another group of atoms is attached, the proportion of said compound being substantially independent ofthe proportion of gelatin.

8. A photographic developing-out gelatino-silver-hahd emulsion of the alkaline type of relatively high light-sensitiveness, comprisin a mixture of the constituents of a gelatin-silver-halid emulsion of lower lightsensitiveness and an added sensitizing compound upon Which depends the difference between said lower and said high light-sensitiveness, said compound having a chemical afiinit-y of silver halid and containing an atom of the sulfur group joined to a single metalloid atom to which at least another group of atoms is attached, the presence of said last named group inducing said chemical afiinity, and the proportion of said compound being substantially independent of j the proportion of said colloid.

9. A photographic developing-out gelatino-silver-halid emulsion of the alkaline type of relatively high light-sensitiveness. comprising a mixture of the constituents of a gclatino-silver-halid emulsion ,of lower light-sensitiveness and an added sensitizing compound upon which depends the dillerence between said lower and said high light sensitiveness, said compound containing a divalent atom of the sulfur group directly joined by a double bond to a single carbon atom to which at least another group of atoms is attached, the proportion of said compound being substantially independentof the proportion of the gelatin.

10. A photographic developing-out gelatino-silver-halid emulsion of the alkaline type of relatively high light-sensitiveness, comprising a mixture of the constituents of a gelatino-silver-halid emulsion of lower light-sensitiveness and a sensitizer comprising thiocarbamid upon which depends the difierence between said lower and said high light-sensitiveness, the proportion of sensitizer being substantially independent of the proportion of gelatin.

11. A photographic developing-out gelatino-silver-halid emulsion of the alkaline type of relatively high light-sensitiveness,

comprising a mixture of the constituents of a gelatino-silver-halid emulsion of lower light-sensitivness and a sensitizer comprising thiosinamine upon which depends the difference between said lower and said high light-sensitiveness, the proportion of sand sensitizer being. substantially independent of the proportion of gelatin.

12. A photographic emulsion comprising a colloid, particles of photographic silver upon which at least part of the light-sen-' sitiveness of the emulsion depends, said compound having a chemical affinity for silver halid and containing an atom of the sulfur group joined to a single metalloid atom to which at least another group of atoms is attached, the presence of said last named group inducing said chemical aflinity, said emulsion being substantially free from sensitizing dye, and the proportion of said compound being substantially independent ofthe proportion of said gelatin.

14. A photographic emulsion comprising gelatin, particles of silver halid suspended therein and an added compound therein upon which at least part of the light-sensitivcness of the emulsion depends, said compound containing a' divalent atom of the sulfur group directly joined by a double bond to a single carbon atomto which at least another group of atoms is attached, the proportion of said compound being substantially independent of the proportion of gelatin, said emulsion being substantially free from sensitizing dye.

15. A photographic developing-out emulsion comprising gelatin, particles of silver halid suspended'therein and an added sensitizer containing thiocarbamid upon which at least part ofthe light-sensitiveness of the emulsion depends, said emulsion being substantially free from sensitizing dye, and the proportion of said compound being sub; stantially independent of the proportionjoi'v said gelatin. A 1

16. A photographic emulsion. comprising gelatin, particles of silver halid suspended therein and an added thiosinamine upon which at least part of the light-sensitiveness of the emulsion depends, said emulsion being substantially free from sensitizing dye, and the proportion of thiosinamine being substantially independent of the proportion of gelatin.

17. A photographic emulsion comprising a colloid, particles'of photographic silver salt suspended therein and an added compound therein upon which at least part. of the light-sensitiveness of the emulsion depends, said compound containing a divalent atom ot'the sulfur group directly joined by a double bond to a single metalloid atom, to which at least another group of atoms is attached, theamount of added compound being less than the order of '10 grains per 130 pounds of emulsion and insulticient to cause immediate fogging tendency.

18. A photographic developing-out emulsion comprising a colloid, particles ot silver halid suspended therein, and an added compound therein upon which at least part of the light-sensitiveness of the emulsion depends, said compound having a chemical affinity for silver halid and containing an atom of the sulfur group joined to'a single metalloid atom to which at least another group of atoms is attached, the presence of said last named group inducing said chemical afiinity, the amount of added compound being less than the order of 10 grains per-130 pounds of. emulsion and insufiicient to cause immediate fogging tendency. i

19. A photographic developing-out emulsion comprising gelatin, particles of silver halid suspended therein, and an added compound therein upon' which atleast part of the light-sensitiveness of the emulsion depends, said compound containing a divalent atom of the sulfur group directly joined by a double bond to a single carbon atom to which at least another group of atoms is attached, the amount of added compound being less than the order. of 10 grains per 1 0 pounds of emulsion and insufficient to cause immediate fogging tendency.

20. A photographic developingout emulsion comprising gelatin, particles of silver halid suspended therein, and an added sensitizer containing thiocarbamid upon which at least part of the light-sensitiveness of the emulsion depends, the amount of added compound being less than the order of 10 grains per 130 pounds of emulsion and insuflicicnt to cause immediate fogging tendency.

21. A photographic developing-out emulsion comprising gelatin, particles of photographic silver salt suspended therein and thiosinamine added therein upon which at least part of .the light-sensitiveness of the emulsion depends, the amount of added compound being less than the order of 10 grains per 130 pounds of emulsion and insuflicient to cause immediate fogging tendency.

22. Aphotographic developing-out emulsion comprising a colloid, particles of photographic silver salt suspended therein and an added, compound therein upon which at of greater density than the set tolerance.

23. A photographic developing-out emulsion comprising gelatin, particles of silver halid suspended therein and an added thiocarbamid upon which at least part of the light-sensitiveness of the emulsion depends, the amount of said thiocarbamid being insufficient to cause fog of greater density than the set tolerance.

24. A- photographic developing-out emulsion comprising gelatin, particles of silver halid suspended therein and an added thiosinamine upon which at least part of the light-sensitiveness of the emulsion depends, the amount of said thiosinamine being insufiicie-nt to cause fog of greater density than the set tolerance.

25. In the process of preparing a developing-out colloid-sensitive-silver-salt emulsion, increasing the light-sensitiveness thereof by incorporating with the other constituents thereof an independent sensitizing compound, said compound containing a divalent atom of thesulfur group directly joined by a double bond to a single metalloid atom to which at least another group of atoms is attached.

26. In theprocess of preparing a developing-out-colloid-sensitive-silver-halid emulsion, increasing the light-sensitiveness thereof by incorporating with the other constituents thereof an indedpendent sensitizing compound which has a chemical aifinity for silver halid and contains an atom of the sulfur group joined to a single metalloid atom to which at least another group ofatoms is attached, the presence of said last named group inducing said chemical affinity.

27. In the process of preparing a developing-out gelatino-silver-halid emulsion increasing the light-sensitiveness thereof byincorporating with the other constituents thereof an independent sensitizing compound containing a divalent atom of the sulfur group directly joined by a double bond to a single carbon atom to which at least another group of atoms is attached.

28. In the process of reparing a devel oping-o it gelatino-silveralid emulsion, in: creasin the light-sensitiveness thereof by incorporating with the other costituents thereof an independent thiocarbamid.

29.- In the process of preparing a developing-out gelatino-silver-halid emulsion, increasing the light-sensitiveness thereof by incorporating independent thiosinamine with the other constituents thereof.

30. In the process of preparing a developing-out colloid-silver-salt emulsion of the alkaline type of relatively high light sensitiveness, combining constituents of a colloidsensitive-silver-salt emulsion of lowerlight sensitiveness with sufiicient independent sensitizing compound to effect high light sen- Sitiveness, said compound containing a divalent atom of the sulfur group directly joined by a double bond to a single metalloid atom to whichat least another group of atoms is attached.

31. In the process of preparing a developing-out gelatino-silver-halid emulsion of the alkaline type of relatively high-lightsensitiveness, combining constituents of a gelatino-silver-halid emulsion of lower light sensitiveness with suflicient independent senmetalloid atom to which at least another.

group of atoms is attached, the-presence of said last named group inducing said chemical aiiinity.

32. {In the process of preparing a developing-out gelatino silver halid emulsion of the alkaline type of relatively high-lightsensitiveness, combining constituents, of a 'elatino-silver-lialid emulsion of said type but of lower sensitiveness with an independent sensitizing compound to effect said lightsensitiveness, said compound containing a divalent atom of the sulfur group directly joined by a double bond to a single carbon atom to which at least another group of atoms is attached.

33. In the process of preparing a developing-out gelatino-silver-halid emulsion of the alkaline type of relatively high light sensitiveness, combining constituents of a .gelantino-silver-halid emulsion of said type but of lower ligh -sensitiveness with an in de-' pendent thiocarbamid to. effect said high light-sensitiveness.

lUll

34. In the process of preparing a develop- .ing-out gelatino-silver-salt emulsion, in-

creasing the light-sensitiveness thereof by incorporating with the other constituents thereof, which are free from sensitizing dye, an independent sensitizing compound, which is free from sensitizing dye, containing a divalent atom of v the sulfur group directly 1 joined by a double bond to a single metalloid atom to which at least another group of atoms is attached.

36. In the process of preparing a developin goat colloid-sensitive-silver-salt emulsion, increasing the light-sensitivenessthereof by incorporating -with the other constituents thereof, which are substantially free from sensitizing dye, an independent sensitizing compound which is substantially free from sensitizing dye, said compound having a chemical affinity for silver halid and containlng'an', atom of the sulfur group joined to a single metalloid atom to which at least another grou of .atoms is attached, the

presence of said last named group inducing thereof 'w ich are substantially free from.

a of atoms is attached.

said chemical aff nity.

37 In the process of preparing a developing-out colloid-sensitive-sil ver-salt emulsion,

increasing the light-sensitiveness thereof by incorporating with the other constituents thereof, which are substantially free from "sensitizing dyes, an independent sensitizing compound, which is alsosubstantially free from sensitizing dye, said compound containing a divalent atom of the sulfur group directly joined by a double bond to a single carbon atom to which at least another group 38. In the process of preparing a developing-out gplatino-silver-halid emulsion, increasing t e light-sensitiveness thereof by incorp'oratin with the other constituents sensitizing dye, an independent thiocarbamid substantially free from sensitizing dye.

39. In the process of preparing a developing-outcolloid-sensitive-silver salt emulsion, increasing the li ht-sensitiveness thereof by incorporating with the other constitutents thereof, which. are substantially free from sensitizing dye, an independent thiosinamine substantially free from sensitizing dye.

40. In the process of preparing a developing-out collold-sensitive silverrsalt emulsion,

increasing the light-sensitiveness thereof by incorporating .with the other constituents thereof an indep'endent sensitlzing compound containing a divalent atom of the sulfur group directly joined by a double bond to a single metalloid atom to which at least another group of atoms is attached, the amount of said added compound being less thanthe order of 10 grains .per. 130 pounds of emulsion and being insufiicient to cause immediate fogging tendency.

41. In the process of preparing a developing-out colloid-sensitive-silver-halid emulsion, increasing the light-sensitiveness thereof by incorporating with the other constituentsthereof an independent sensitizing compound which has'a chemical afiinity-for silver halid'and contains an atom of the sulfur group joined to a single metalloid atom to which at least another group of atoms is attached, the presence of said last named'group inducing said chemical afiinity, the amount of said added compound being less than the order of 10 grains per 130 pounds of emulsion and insuflicient to cause immediate fogging tendency.

43. In the process of preparing a developing-out gelatino-silver halid-emulsion, in-

creasing the light-sensitiveness thereof by incorporating with the otherconstituents thereof an independent sensitizing compound containing a divalent atonof the sulfur group directly joined by a double bond to a single carbon atom to which at least another group of atoms is attached, the amount of said added compound being less than the order of 10 grains per. 130

pounds of emulsion and insuflicient to cause immediate fogging tendency.

, 44. In the process of preparing a developing-out gelatino-silver-halid emulsion, increasing the light-sensitiveness thereof by incorporating'with the other constituents thereof an independent thiocarbamid, the amount of said added compound being less than the order of 10 grains per 13) pounds of emulsion and insufficient to cause fogging tendency.

45. In the process of preparing a developing-out gelatino-silver-halid emulsion, in-.

creasing the light-sensitiveness thereof by incorporating an independent thiosinamine with the other constituents thereof, the

amount of said added compound being less than the order of 10 grains per 130 pounds of emulsion and insufficient to cause i'mmediate fogging tendency. v

46. The process of preparing photographic gelatino-silver-halid emulsions, which comprises substantially freeing gelatin from any sensitizing compounds originating therein, mixing an independent sensitizingv compound therein, and preparing a sensitive photographic emulsion from said mixture.

47. The process which comprises incorporating in a melted developing-out gelati no-silver-halid emulsion an 'independent sensitizing compound containing a divalent atom of the sulfur group directly joined by a double bond to a single metalloid atom to which at least another group of atoms is,

attached.

4 In the process of preparing a developing-out gelatino-silver-halid emulsion, mixing with the gelatin an independent sensitizing compound containing a divalentatom of the sulfur group directly joined by a double bond to a single metalloid atom to which at least another group of atoms is attached and thereafter incorporating said mixture with the other ingredients of said emulsion.

49. In the process of making a photographic colloid-sensitive-silver-salt emulsion, incorporating with the other ingredients thereof an added compound upon which at I least part of the light-sensitivenestof the suliicient to cause fog o photographic emulsions,

emulsion-forming colloid having incorporated therein an independent sensitizing compound containing a divalent atom of the sulfur group directly joined by a double bond, to a single metalloid atom to which at least .another group of atoms is attached.

51. An intermediate for use in making photographic emulsions,- comprising an emulsion-forming colloid having incorporated therein an independent sensitizing compound, said compound having a chemical aflinity for silver halid and containing an atom of the sulfur group joined to a single metalloid atom to which at least another groupof atoms is attached, the pressaidlast named group inducing said chemical affinity. 52. An inte'rmediate for use in making photographic emulsions, comprising gelatin having incorporated therein an independent sensitizing compound, containing a divalent atom of the sulfur group directly joined to O -a single carbon atom to which at least another group of atoms is attached.

53. An intermediate for use in making photographic emulsions, comprising gelatin having incor orated therein an independent thiocarbami i.

54. An intermediate for use in making of gelatin.

photographic emulsions, comprising gelatin having incorporated therein independent thiosinamine.

55. An intermediate for use in making photographic emulsions, comprising .an emulsion-forming colloid having incorporatedtherein an independent sensitizing compound containing a divalent atom of the sulfur group directly joined by a double bond to a single metalloid atom to which at least another group of atoms -is; attached, the amount of said added compound being less than the order of 10 grains in 100 ppunds of gelatin. i

56. An intermediate for use in making photographic emulsions, comprising an emulsion-forming colloid having incorporated therein an independent sensitizing compound, said compound having a chemical affinity for silver halid and containing an atom of the sulfur ,group joined to a single metalloid atom to which at least another group of atoms is attached, the presence of said last named group inducing said chem.- ical aflinity, the amount of said added compound being less than the order of 10 grains in 100 pounds of gelatin.

57. An intermediate for use in making photographic emulsions, comprising gelatin having incorporated therein an independent sensitizing compound "containing a divalent atom of the sulfur group directly joined to a single carbon atom to which at least another group of atoms is attached, the amount of said added compound being less than the order of 10 grains in pounds 58. An intermediate for use in making photographic emulsions, comprising gelatin having incor orated therein an independent thiocarbamid: the amount of said added compound being less than the order of 10 grains in 100 pounds of gelatin.

59. An intermediate for. use in making photographic emulsions, comprising gelatin having incorporated therein thiosinamine, the amount of said added compound being less than the order of 10 grains in 100 pounds of gelatin.

60. An intermediate for use in making photographic developing out emulsions, comprising a mixture of gelatin and an independent sensitizing com ound containing a divalent atom of the su fur group directly joined by a double bond to'a single metalloid atom,'to which at least another group of atoms is attached, the proportion. of said compound being insufficient to cause fog density exceeding the set tolerance when said intermediate is made into said developing- 1 (32. An intermediate for use in making photographic developing-out emulsions, com-- prising gelatin and independent thiosinamine, the amount of thiosinamine being insufficient to cause fog density exceeding the set tolerance when said intermediate is made up into said emulsions. I

63". The process of making an intermediate for use in the preparation of photographic emulsions, which comprises incorporating in an emulsion-forming cololid an independent sensitizing compound containing a divalent atom of the sulfur group directly joined by a double bond to a single metalloid atom to which at least another group of atoms is attached.

64. The process of making an intermediate for use in the preparation of photographic emulsions, which comprises incorporating in an emulsion-forming colloid an independent sensitizing compound, said compound having a chemical affinity for silver halid and containing an. atom of the sulfur group joined by a single metalloid atom to which at least another group of atoms 1s attached,

the presence of saidlast named'group inducing said chemical afiinity.

65. The process of making an intermediate for usein the preparation of photographic emulsions, which comprises incorporating in gelatin an independent sensitizing compound containing a divalent atom ofthe sulfur group directly joined to a single carbon atom to which at least another group of atoms is attached.

66. The process of making an intermediate for use in the preparation of. photographic .emulsions, which comprises adding to an emulsion-forming colloid an independent thiocarbamid.

67. The process of. making anintermediate for use in the preparation of photographic emulsions, which comprises addingto .an emulsion-forming colloid independent thiosinamine.

68. The process of making anintermediate for use in the pre aration of photographic emulsions, whicii comprises incorporating in an emulsi'on-forming' colloid an independent sensitizing compound containing a divalent atom of the sulfur group di rectly joined by metalloid atom to which at least another group of. atoms is attached, the amount of said added compound being less LAD the order of 10 grains per 1 pounds of'said colloid (calculated as dry colloid) and being insufficient to cause immediate fogging tendency.

69. Theprocess of making an intermediate for use in. the preparation of photoa double bond to a single graphic emulsions, which comprises incorporating man emulsion-forming colloid an -lI1 dependent sensit zing compound, said compound having a chemical aflinity for silver amount of said added compound being less than the order of 10 grains per 100 pounds of said colloid (calculated as dry colloid) and being insufiicient to cause immediate fogging tendency.

70. The process of making an intermediate for use in the preparation of photo graphic emulsions, which comprises incorporating in gelatin a sensitizing compound containing a divalent atom of the sulfur group directly joined to a single carbon atom of which at least another group of atoms is attached, the amount of said added compound being less than the order of 10 grains per 100 pounds of said colloid (cal-' culated as dry' colloid) and being insuflicient to cause immediate fogging tendency.

71. The'process of making an intermediate for use in the preparation of photographic emulsions, which comprises adding to an emulsion-forming colloid a thiocar- 9 bamid, the amountof said added compound being less than the order of 10 grains per 100 pounds of saidcolloid (calculated as dry colloid) and being insuflicient to cause immediate fogging tendency.

. T2. The process of making an intermediate for use in the preparation ofphotos graphic emulsions, which comprises adding to an emulsion-forming colloid a thiosina mine, the amount of said added compound being less than the order of 10 grains per pounds of said colloid (calculated as dry colloid) and being insufiicient to cause immediate fogging tendency.

73..The process of making an intermediate for use in the preparation of photographic emulsions, which comprises incorporating in an emulsion-forming colloid an independent sensitizing compound containing a divalent atom of the sulfur group directly joined by a double bond to asingle metalloid atom to which at least another group of atoms is attached, the proportion of said porating therein an independent sensitizing compound. 1

75,. The process of making. an intermediate for use in the preparation of photographic 'gelatino silver 4 halid emulsions,

4 which comprises substantially freeing gelatin frpm sensitizing compounds and incoi'porating therein a sensitizlng compound con-,- group taining a divalent atom of the sulfur 5 directly 'oined by a double bond to a single metalloid atom to which at least another group of atoms attached, the amount of said added compound being less than the order of 10 grains per 100 pounds of said gelatin insufiicient to cause immediate fogging tendency. 1

Signed at'Rochester, New York, this 4th day of June, 1924.

, SAMUEL E. SHEPPARD.-

(calculated as dry gelatin) and being 10 

